Explosive formulations based upon mixtures of particulate aluminum fuels in admixture with a liquid containing an oxidizing agent, which may be in the form of a solution or an emulsion, are well known in the art. For let, U.S. Pat. No. 5,007,973 to Trapp et al., discloses the formulation of an explosive composition from two liquid components which are, in themselves, not explosives. One component contains a finely divided metal fuel, preferably, aluminum, in a carrier liquid such as a polyhydric alcohol, e.g., ethylene glycol, and a pyrrolidone solvent. The carrier liquid contains a thickening agent which functions to impart thixotropic rheological properties to the suspension of particulate fuel. The oxidizing agent is an aqueous solution of an inorganic oxidizing salt such as an alkali metal or alkaline earth metal nitrate or perchlorate. The preferred oxidizing salt disclosed in the Trapp et al. patent is sodium perchlorate, either alone or in admixture with another oxidizing salt. The oxidizing liquid can contain microcells such as glass or plastic microbubbles or the like, which function to lower the density and sensitize the ultimate explosive formulation. In the Trapp et al. procedure, both the aluminum fuel particles and the microcells are of relatively small size. For example, the aluminum fuel has an average particle size within the range of 5-100 microns, thus providing a relatively high surface to volume ratio for the aluminum particles. While the explosive formulation in the Trapp et al. procedure provides a powerful high explosive after mixing, the individual components before mixing are relatively safe, pumpable liquids. Thus, the explosive formulations of the Trapp et al. patent are useful in military and non-military operations where it is desirable to blast ditches such as "tank traps" or fire break lines for the control of forest fires.
U.S. Pat. No. 3,344,743 to Griffith, discloses another procedure, for formulating blasting slurries which can be made at the blasting site from relatively safe component parts. Here, a metal fuel component such as aluminum is an optional additive. The aluminum can be added in the form of a powder or flake or as atomized in an amount within the range of about 0.5-15% of the total formulation. In the Griffith patent the oxidizing agent can take the form of alkali or alkaline earth metal chlorates, perchlorates or nitrates, preferably in admixture with ammonium nitrate.
Another procedure for the on-site formulation of slurry explosive compositions, which can include particulate aluminum as a fuel, is disclosed in U.S. Pat. No. 4,207,125 to Grant. Here, one component is a highly viscous or paste-like liquid phase which can contain one of the inorganic oxidizing salts such as an ammonium, alkali metal or an alkaline earth metal, nitrates, chlorates, perchlorates, peroxides or sulfates, which are known to function as oxidizers in explosive reactions. Freezing point depressants such as ethylene glycol, propylene glycol, glycerol and formamide, are used not only to depress the freezing point of the slurry formulation, but also to provide an optimum consistency. Thickening agents used in the oxidizing component include high molecular weight polysaccharides or polyacrylamides. At the detonation site, the liquid pre-mixed phase is combined with an appropriate particulate material to produce a slurry explosive. The particulate material can include granulated or prilled ammonium nitrate and aluminum or magnesium metal with a particle size ranging from about 4 to 200 mesh. By way of example, 6 pounds of a thick sodium nitrate solution was stored for 35 days and then combined with 10 pounds of prilled ammonium nitrate, followed by agitation and then by the addition of 4 pounds of particulate aluminum having a particle size of +100 mesh and a thickness of 0.25 mills (Reynolds HPS-10), and the mixture then agitated to provide an explosive formulation having a density of 1.1 grams per cubic centimeter. The resulting slurry was detonated in a metal can with a pentolite charge.
An alternative approach to the formulation of binary explosives from non-detonable components is found in U.S. Pat. No. 2,892,377 to Davidson. Davidson discloses the mixing of the non-explosive components in a container. Thus, a cylindrical sheet metal canister is filled with ammonium nitrate particles. The canister is closed at its upper end with a wall structure having a central rubber pad. In order to form the blasting package, a syringe is employed to pierce the rubber pad and discharge an appropriate quantity of a non-explosive liquid organic fuel into the body of ammonium nitrate particles. The liquid fuel may contain a surfactant to reduce the surface tension between the ammonium nitrate and the liquid fuel. By way of example, from 92-95 parts of ammonium nitrate may be injected with 8 parts of orthonitrotoluene or 5 parts of hydrocarbon oil, respectively, to produce the blasting cartridge.
A similar approach, based upon the use of solid particulate oxidizing agents, is disclosed in U.S. Pat. No. 3,926,119 to Hurst et al. Here, a two-compartment container is employed which is divided by a porous partition into a lower primary charge chamber and an upper secondary, charge chamber. The charge chambers contain a particulate oxidizing component such as one or more alkali and alkaline earth metal nitrates, ammonium nitrate, alkali and alkaline earth perchlorates and ammonium perchlorate. The solid component in the primary chamber has a particle size less than 3,000 microns and preferably, about 5-250 microns. The secondary chamber can contain larger particle sizes, in the range of 0.5-10 millimeters, preferably, about 2 millimeters. Microballoons can be present as sensitizing agents in both chambers. The canister containing the particulate oxidizing material is armed by the addition of a liquid hydrocarbon containing bonded nitrogen in a positive valence state which is detonable, but non-cap sensitive. Where two separate chambers, as described previously are involved, a preferred liquid component is about 60-100 percent nitromethane, which, if pure nitromethane is not employed, can be mixed with up to 40 wt. % of higher nitroalkanes having 2 or 3 carbon atoms or various halogenated or nitroaromatic compounds, Where only one chamber is employed in the canister, the charging liquid component would contain at least 75% nitromethane. The explosive charge, when assembled, is detonable by a number 6 blasting cap.